Abstract
Malignant transformation of intestinal endometriosis is extremely rare, and only eight cases have been reported in Japan, including the present case. A case of malignant transformation of rectal endometriosis is reported. The patient was a 48-year-old woman with a positive fecal occult blood test. Colonoscopy showed a flat elevation accompanied by mucosal abnormality in the upper rectum. Computed tomography (CT) and magnetic resonance imaging (MRI) showed wall thickening, 5 cm in length, in the upper rectum, as well as an ovarian cyst in the left ovary and massive uterine fibroids. Based on these and biopsy findings, a malignant tumor resulting from intestinal endometriosis was diagnosed. Laparotomy showed the massive uterine fibroids and the left ovarian cyst forming a single mass, as well as closure of the pouch of Douglas due to severe adhesions caused by endometriosis ; therefore, hysterectomy with bilateral adnexectomy and lower anterior resection were performed. On histopathological examination, the patient was diagnosed with endometrioid adenocarcinoma that developed from ectopic endometrium primarily located in the muscularis propria layer and the submucosal layer. TC (Paclitaxel+Carboplatin) therapy was given as adjuvant chemotherapy, and the patient has survived without recurrence for 18 months.
